Biological Rhythms Flashcards
What is an infradian rhythms?
A biological rhythm with a frequency of less than 24 hours
What is an example of an infradian rhythms
The Menstrual Cycle - lasts for 28 days
Explain research into the influences on menstrual cycles
McClintock (1998) wanted to test if menstrual cycles would synchronise as a result of the influence of female pheromones
29 women with a history of irregular periods. Samples of pheromones were gathered form 9 of the women at different stages of their menstrual cycles via a cotton pad placed in their armpits for 8 hours.
The pads were treated with alcohol and frozen to be rubbed on the upper lip of the other participants
They found that 68% of women experienced changes to their cycle of their odour donor
Evaluate the findings of McClintock’s study
Some would argue that Mclintock’s findings make evolutionary sense
It was seen as possibly advantageous for females to menstruate together and therefore fall pregnant around the same as the result could be new born babies being cared for collectively.
This will increase the chances of the offspring’s survival.
Evaluate the methodological issues with the synchronisation study
The methods employed of the early synchronisation has been criticised. Commentators argue confounding variables that may affect change in a women’s menstrual cycle such as stress, exercise and changes in diet may have been present. This means that any supposed pattern of synchronisation as seen in the studies by McClintock is no more than would have been expected to occur by chance showing a lack of replicability from the studies.
Explain the infradian rhythms: Seasonal Affective Disorder
Seasonal Affective Disorder (SAD) is a depressive disorder which has a seasonal onset.
Triggered during the winter months as the day light hours decreases
This is because the pineal gland which secretes melatonin, during winter increases the levels of melatonin as there is a lack of lightand decreases serotonin levels which responsible for mood regulation.
How can SAD be treated?
Phototherapy: Involves a light box stimulating very strong light in the morning and evening for around 30 mins
This is done in order to reset melatonin levels
Evaluate the research into the effectiveness of phototherapy
Eastman et al found that phototherapy is an effective treatment which stimulates strong light in the morning and evening. This was seen to relieve symptoms in up to 60% of sufferers
Counter Argument:
However the same study recorded a placebo effect of 30% using a sham negative iron generators which casts doubt on the chemical influence of phototherapy.
It is therefore hard to conclude whether the therapy itself or the expectation of treatment led to improvements in symptoms.
What is an ultradian rhythm?
A biological rhythm with a frequency of more than one cycle in 24 hours
What is an example of an ultradian rhythm?
The sleep cycle is 90 minutes in total and goes through 5 stages. Each stage is characterised by different brain wave activity.
Explain supporting research for the sleep cycle
Dement & Kleitman used EEG’s to investigate sleep stages on 9 humans in a sleep lab.
They found out that R.E.M. activity was highly correlated with the experience of dreaming, participants were woken during REM sleep and reported very accurate recall of their dreams.
Replicating of this investigation have noted similar findings though the small size of the original sample has been criticised by some
This study suggests that REM(dream) sleep is an important component of the ultradian sleep cycle.
